# add the library that runs
add_library(MathFunctions MathFunctions.cxx)

# state that anybody linking to us needs to include the current source dir
# to find MathFunctions.h, while we don't.
target_include_directories(MathFunctions
                           INTERFACE 
                           $<BUILD_INTERFACE:${CMAKE_CURRENT_SOURCE_DIR}>
                           $<INSTALL_INTERFACE:include>
                           )

# should we use our own math functions
option(USE_MYMATH "Use tutorial provided math implementation" ON)
if(USE_MYMATH)

  target_compile_definitions(MathFunctions PRIVATE "USE_MYMATH")

  # first we add the executable that generates the table
  add_executable(MakeTable MakeTable.cxx)
  target_link_libraries(MakeTable PRIVATE tutorial_compiler_flags)

  # add the command to generate the source code
  add_custom_command(
    OUTPUT ${CMAKE_CURRENT_BINARY_DIR}/Table.h
    COMMAND MakeTable ${CMAKE_CURRENT_BINARY_DIR}/Table.h
    DEPENDS MakeTable
    )

  # library that just does sqrt
  add_library(SqrtLibrary STATIC
              mysqrt.cxx
              ${CMAKE_CURRENT_BINARY_DIR}/Table.h
              )

  # state that we depend on our binary dir to find Table.h
  target_include_directories(SqrtLibrary PRIVATE
                             ${CMAKE_CURRENT_BINARY_DIR}
                             )

  # state that SqrtLibrary need PIC when the default is shared libraries
  set_target_properties(SqrtLibrary PROPERTIES
                        POSITION_INDEPENDENT_CODE ${BUILD_SHARED_LIBS}
                        )

  target_link_libraries(SqrtLibrary PUBLIC tutorial_compiler_flags)
  target_link_libraries(MathFunctions PRIVATE SqrtLibrary)
endif()

target_link_libraries(MathFunctions PUBLIC tutorial_compiler_flags)

# define the symbol stating we are using the declspec(dllexport) when
#building on windows
target_compile_definitions(MathFunctions PRIVATE "EXPORTING_MYMATH")

# install rules
# 只有运行make install才会安装在<prefix>/lib or <prefix>/include
# <prefix>的值默认为/usr/local，如果设置CMAKE_INSTALL_PREFIX的值，
# 则安装在${CMAKE_INSTALL_PREFIX}/lib or ${CMAKE_INSTALL_PREFIX}/include目录下
install(TARGETS MathFunctions DESTINATION lib)
install(FILES MathFunctions.h DESTINATION include)


# library that just does sqrt
add_library(myString STATIC
  my_string.cxx
)

# state that we depend on our binary dir to find Table.h
target_include_directories(myString PRIVATE
               ${CMAKE_CURRENT_BINARY_DIR}
               )


set(installable_libs MathFunctions tutorial_compiler_flags)
if (TARGET SqrtLibrary)
  list(APPEND installable_libs SqrtLibrary)
endif()

install(TARGETS ${installable_libs} myString
        EXPORT MathFunctionsTargets
        DESTINATION lib)

install(FILES MathFunctions.h DESTINATION include)

install(FILES my_string.h DESTINATION include)

include(CMakePackageConfigHelpers)
configure_package_config_file(${CMAKE_SOURCE_DIR}/Config.cmake.in
  "MathFunctionsConfig.cmake"
  INSTALL_DESTINATION "lib/cmake/example"
  NO_SET_AND_CHECK_MACRO
  )

 # generate the version file for the config file
write_basic_package_version_file(
  "MathFunctionsConfigVersion.cmake"
  VERSION "0.1"
  COMPATIBILITY AnyNewerVersion
)

# install the configuration file
install(FILES
  ${CMAKE_CURRENT_BINARY_DIR}/MathFunctionsConfig.cmake
  ${CMAKE_CURRENT_BINARY_DIR}/MathFunctionsConfigVersion.cmake
  DESTINATION lib/cmake/MathFunctions
)

install(EXPORT MathFunctionsTargets
        FILE MathFunctionsTargets.cmake
        NAMESPACE MathFunctions::
        DESTINATION lib/cmake/MathFunctions
)

# 可以在cmake --build build这一步直接生成MathFunctionsTargets.cmake，不用等到cmake --install build/
# MathFunctionsTargets.cmake
# 下面两句直接可以在另外一个工程中使用ｆｉｎｄ_package，但是需要先设置CMAKE_PREFIX_PATH的路径
# 否则会出现
# https://cmake.org/cmake/help/latest/guide/importing-exporting/index.html#using-the-package-configuration-file
# 这段教学最后的错误
#　A warning may have appeared during CMake configuration:

# CMake Warning at CMakeLists.txt:4 (find_package):
# By not providing "FindMathFunctions.cmake" in CMAKE_MODULE_PATH this
# project has asked CMake to find a package configuration file provided by
# "MathFunctions", but CMake did not find one.

# Could not find a package configuration file provided by "MathFunctions"
# with any of the following names:

#   MathFunctionsConfig.cmake
#   mathfunctions-config.cmake

# Add the installation prefix of "MathFunctions" to CMAKE_PREFIX_PATH or set
# "MathFunctions_DIR" to a directory containing one of the above files.  If
# "MathFunctions" provides a separate development package or SDK, be sure it
# has been installed.
# Set the CMAKE_PREFIX_PATH to where MathFunctions was installed previously and try again. Ensure that the newly created executable runs as expected.
# set(CMAKE_PREFIX_PATH ${PROJECT_BINARY_DIR}/MathFunctions)

export(TARGETS ${installable_libs} myString
  NAMESPACE MathFunctions::
  FILE MathFunctionsTargets.cmake
)

export (PACKAGE MathFunctions)
